In recent years, in order to meet the demand for preventing global warming by cutting CO2 exhaustion, electrically driven automobiles are being actively marketed. In addition to conventional sedans and motorbikes, companies are developing electrically driven buses, trucks and other large size vehicles.
Accordingly, there has been a demand for developing technology for quickly charging battery packs carried on electrically driven automobiles. In order to realize this, in the related art, a quick charger have been proposed. If charging can be carried out at up to 50 kW by the quick charger, an onboard battery pack of about 24 kWh can be nearly fully charged in about 30 min.
However, for large size vehicles, the energy needed for running is higher than that for sedans, so that the capacity of the battery pack carried on such vehicles is naturally higher. When a high capacity onboard battery pack is charged by using the conventional quick charger, due to the restriction on maximum output power and maximum current, it is difficult to fully charge in a short time. For example, for a 50 kWh onboard battery pack, it takes about 1 hour to charge it with the quick charger.
Buses, trucks and other large size vehicles run according to their predetermined round schedules, respectively. When it takes a long time to charge the onboard battery pack, it is difficult to make sufficient charging for the battery pack between two rounds of running along the round schedule. In such a case, it is necessary to use more large size vehicles to realize the related round schedule. As a result, the operation efficiency decreases.